arm64: mm: Test for pmd_sect() in vmemmap_check_pmd()

arm64: mm: Test for pmd_sect() in vmemmap_check_pmd()

Commit 2045a3b8911b ("mm/sparse-vmemmap: generalise vmemmap_populate_hugepages()")
introduces the vmemmap_check_pmd() while does not verify if the entry is a
section mapping, as is already done for Loongarch & X86.
The update includes a check for pmd_sect(). Only if pmd_sect() returns true,
further vmemmap population for the addr is skipped.

Signed-off-by: Zhenhua Huang <quic_zhenhuah@quicinc.com>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Link: https://lore.kernel.org/r/20250102074047.674156-1-quic_zhenhuah@quicinc.com
Signed-off-by: Will Deacon <will@kernel.org>